Any suggestions on keeping the coach cool for passengers during the summer other than keeping the engine A/C fan on high and running the generator to use the roof unit?
If you don't like the heat and humidity in the southern states in the summer, don't travel there. There are wheels under the rigs that can go anywhere. Travel in the north or at higher elevations for the summer.
BTW - we've been in 100+ heat with 95% humidity and didn't have a problem keeping our coach cool, even at a site with no shade. Maybe the problem is lack of insulation in your rig?